Installation of seatbelt apparatuses in automobiles is compulsory to ensure safety of drivers/passengers. When a driver/passenger operates a seatbelt apparatus to set a seatbelt (i.e., the webbing), the webbing may cause a so-called “hanging” state depending on the sitting height of the driver/passenger. To prevent such a hanging state and ensure a comfortable ride, a variety of shoulder adjuster apparatuses, which are capable of adjusting the height of a webbing anchor according to the sitting height of a driver/passenger, have been proposed.
Examples of shoulder adjuster apparatuses of this type include a seatbelt anchor apparatus and a webbing anchor apparatus that were proposed by the present inventor as shoulder adjuster apparatuses, and are disclosed in Japanese Unexamined Patent Application Publications Nos. 2-279445, 5-294208, and 2001-341614.
In known shoulder adjuster apparatuses, however, a strong impact force applied to a webbing anchor may cause a large impact load on the shoulder adjuster apparatus, deformation of the shoulder adjuster apparatus due to a heavy load particularly exerted on an engaging portion between an adjusting base and a sliding base, damage to the adjusting base and the sliding base, and impairment of adjusting function due to the deformation of the shoulder adjuster apparatus.
Moreover, the deformation of the shoulder adjuster apparatus due to a heavy load being exerted on the engaging portion between the adjusting base and the sliding base causes the adjusting base to be detached from the sliding base, the adjusting function of the shoulder adjuster apparatus to be impaired, and the shoulder adjuster apparatus to be disabled.
To provide a safer shoulder adjuster apparatus, a crucial issue that has been recognized is to improve the shape of the engaging portion between the adjusting base and the sliding base such that the strength thereof can be improved.
To adjust the height of the webbing anchor according to the sitting height of a driver/passenger, a latch mechanism needs to be pulled out against the elastic force of a spring.
However, to fix the shoulder adjuster apparatus at a desired height, this spring has a spring constant sufficient for preventing problems, such as detachment of a latch pin caused by vibrations or the like. Therefore, pulling out a button requires a large amount of force and cannot necessarily be performed easily by a drivers/passengers sitting in a seat. Thus, since the latch mechanism of the known shoulder adjuster apparatus does not have sufficient operability for adjusting the height of the webbing anchor, there has been a demand for the development of a mechanism capable of tightly securing the webbing anchor while exhibiting excellent operability in terms of adjusting the height of the webbing.
Moreover, in the latch mechanism of the known shoulder adjuster apparatus, it is assumed, in some rare cases, that vibrations and impacts cause a button section to malfunction because of the structure of a fixed button. It has also been pointed out that this may cause the latch pin to be pulled out of a lock hole and change the height of the webbing anchor while riding in the car. A strong impact force applied to the shoulder adjuster apparatus from one direction, particularly at the time of impact, causes the shoulder adjuster apparatus to malfunction.
There is also a possibility that the height of the webbing anchor may be changed at the time of impact, because an air bag installed in the car for ensuring the safety of drivers/passengers presses the shoulder adjuster apparatus from one side, thus causing the shoulder adjuster apparatus to malfunction. Therefore, improved stability of a button, which serves as an operating section, has been demanded to improve vibration resistance and impact resistance of the latch mechanism.
Moreover, vibrations while the car is moving bring the latch pin and a lock hole into contact, which produces metallic noises. In the known shoulder adjuster apparatus, to reduce such metallic noises caused by contact, the tip of the latch pin is coated with a resin or provided with an O-ring for noise reduction. This increases the number of components required to form the shoulder adjuster apparatus and causes an increase in material costs and production costs.
The present invention is made in view of the circumstances described above and aims to provide a shoulder adjuster apparatus having excellent shock absorbency, capable of preventing degradation of performance due to deformation and the like, and having excellent safety characteristics.
Another object of the present invention is to provide a shoulder adjuster apparatus in which a latch mechanism installed therein offers improved impact resistance and vibration resistance to prevent malfunctioning, and in which a webbing anchor ensures its stability when it is fixed, which improves its operability during the height adjustment.
Another object of the present invention is to provide a shoulder adjuster apparatus in which contact noise produced from a latch pin and a lock hole of the latch mechanism installed in the shoulder adjuster apparatus is reduced.